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<title>Histogram Refinement for Content-Based Image Retrieval</title>
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<h1>Histogram Refinement for Content-Based Image Retrieval</h1>

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<!WA0><!WA0><!WA0><!WA0><a href="http://www.cs.cornell.edu/home/gregpass/welcome.html">Greg
Pass</a><br>
<!WA1><!WA1><!WA1><!WA1><a href="http://www.cs.cornell.edu/home/rdz/rdz.html">Ramin Zabih</a><br>
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<h2>Abstract</h2>

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Color histograms are widely used for content-based image retrieval.
Their advantages are efficiency, and insensitivity to small changes in
camera viewpoint.  However, a histogram is a coarse characterization
of an image, and so images with very different appearances can have
similar histograms.  We describe a technique for comparing images
called histogram refinement, which imposes additional constraints on
histogram based matching.  Histogram refinement splits the pixels in a
given bucket into several classes, based upon some local property.
Within a given bucket, only pixels in the same class are compared.  We
describe a split histogram called a color coherence vector (CCV),
which partitions each histogram bucket based on spatial coherence.
CCV's can be computed at over 5 images per second on a standard
workstation.  A database with 15,000 images can be queried using CCV's
in under 2 seconds.  We demonstrate that histogram refinement can be
used to distinguish images whose color histograms are
indistinguishable.



<p>

A paper entitled <b>Histogram Refinement for Content-Based Image
Retrieval</b> will appear in the Workshop on the Applications of
Computer Vision.  This paper is available in PDF format <!WA2><!WA2><!WA2><!WA2><a
href="http://www.cs.cornell.edu/home/rdz/wacv-final.pdf">here</a>.
Free PDF readers can be obtained for many platforms from <!WA3><!WA3><!WA3><!WA3><a
href="http://www.adobe.com">Adobe</a>.

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A slightly older paper entitled <b> Comparing Images Using Color
Coherence Vectors</b> will appear in the 1996 ACM Conference on
Multimedia, and is available in PDF format <!WA4><!WA4><!WA4><!WA4><a
href="http://www.cs.cornell.edu/home/rdz/mm96-final.pdf">here</a>.

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<ADDRESS>
<I>rdz@cs.cornell.edu,<br> gregpass@cs.cornell.edu<BR>
Monday, July 23 1996
</I>
</ADDRESS>

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